A chip package may usually include a chip, a metal contact structure electrically contacting the chip, and packaging material at least partially enclosing the chip and the metal contact structure. The metal contact structure may provide an electrically conductive connection to the chip from outside the packaging material. The metal contact structure may include a bond wire, which may include or consist of copper (Cu). Bond wires made of bare Cu material may have a significant cost advantage compared to gold (Au) wire, which has been, and still is, the main wire material used. However, Cu wire may have some technological disadvantages and drawbacks, which hindered its rapid usage and industrial acceptance. For example, copper is easily oxidized at ambient air. Therefore, its shelf life time is very limited and strict rules may be applied in assembly fabs (e.g. shipment in sealed packages with inert media, limited hours of usage once the sealed package is opened, etc.).
Furthermore, Cu bond interconnects may often and more easily (e.g. more easily than interconnects using gold wire) undergo corrosion in stress tests using moisture levels (e.g. Temperature Humidity Bias (THB), Highly Accelerated Stress Test (HAST), Unbiased Temperature/Humidity Accelerated Stress Test (UHAST), or Unbiased Temperature/Humidity Autoclave (AC)).
And yet furthermore, Cu wedge bond interconnects may show weak bonding and adhesion, especially on surfaces which are coated with noble metals (e.g. gold (Au), silver (Ag), or palladium (Pd)) and which have a smooth, not roughened surface.
Similar drawbacks may occur for silver (Ag) wires used as bond wires.